Jane Birkin, Marion Cotillard, and More Jean Queens of Cannes

Despite its proximity to the beach and the Riviera’s reputation as a playground for the rich and beautiful, the Cannes Film Festival is a grown-up, dress-up affair complete with formal dress requirements. For gala screenings, black-tie is required of men, and women are expected to wear heels. Still, it’s not all work and no play for the film community in the month of May: Cannes’s photo calls are sun-kissed and relatively informal events. Yet this past Sunday, when From the Land of the Moon actress Marion Cotillard showed up to one in a head-turning getup, it didn’t go unnoticed that her black Filles à Papa minidress was made of (gasp) denim. (She played to the book later in the evening, becoming a living Oscarette in a draped-back metallic Dior column.)

It’s not that denim, ubiquitous everywhere else (including the closest airport, in Nice), is unknown in Cannes—denim started making inroads into female film-festival attire in the late 1960s thanks to Jane Birkin and Geraldine Chaplin—it’s just that it has remained mostly an off-duty look. Here, 15 celebs who have dared to go casual in Cannes and made denim work in their favor.